ORLANDO - A gunman opened fire at a gay night club in Orlando, Florida, early Sunday, killing 50 people and wounding 53 more before he was killed in a shootout with SWAT team members. Authorities say he may have had a connection with radical Islamic terrorism. Here's what we know about the deadliest mass shooting in U.S. history:

MASS CASUALTIES:

At least 50 people are dead, and 53 were hospitalized, most in critical condition, officials said. A surgeon at Orlando Regional Medical Center said the death toll was likely to climb.

The city of Orlando is publishing the names of those killed on its website after their families have been contacted. The city's website includes the #PrayforOrlando hashtag and says officials are "working tirelessly" to get information to families. The list can be found here.

Sunday night, workers brought four bodies on stretchers out of club Pulse and loaded them into white vans. The action was repeated over and over.

The bodies were then taken to the Orange County Medical Examiner's office.

THE SHOOTER:

Authorities identified the shooter as 29-year-old Omar Mateen of Port St. Lucie, Florida. His father, Seddique Mateen, told NBC News that his son got angry when he recently saw two men kissing in Miami a couple of months ago. Seddique said the attack had nothing to do with religion.

Mateen's father is a native of Afghanistan who appears on a television program on broadcast on a California channel.

The show is known for "its anti-US tirades" and "pro-Taliban" remarks that are broadcast in the Dari language, according to a former Afghan official. 

Omar Mateen had been licensed as a private security officer in Florida. Records show he held the firearms license since at least 2011.

Ronald Hopper of the FBI says Mateen was an American citizen. Hopper says Mateen purchased at least two firearms legally within the last week or so.

A law enforcement official says Mateen made a 911 call from the club, professing allegiance to the leader of the Islamic State, Abu Bakr al-Baghdadi.

Hopper says some 911 calls involving the shooter and the massacre have become federal evidence. He says the conversations involved the Islamic State.

Hopper says the shooter in 2013 made inflammatory comments to co-workers , and that Mateen was interviewed twice. Hopper calls those interviews inconclusive.

In 2014, Hopper says, officials found that Mateen had ties to an American suicide bomber. Hopper describes the contact as minimal; it did not constitute a threat at that time.

He was cleared after both investigations.

The top Democrat on the House Intelligence Committee says investigators have not yet found evidence of direct communication between Mateen and Islamic State members overseas. Rep. Adam Schiff says it is possible that Omar Mateen was self-radicalized but not "under the command and control of ISIS."

Mateen's ex-wife, Sitora Yusifiy says Mateen was bipolar and also had a history with steroids.

She says that in the four months they were together he cut her off from her family and regularly beat her. She says that her family visited her and saw she wasn't OK and rescued her from the situation.

Yusifiy says they literally pulled her out of his arms. She says she left all her belongings and has had no contact with him for seven or eight years.

She says Mateen was religious, but she saw no signs of radicalism.

Of the nightclub massacre she says, "there was no sign of any of this at all."

ACT OF TERROR?:

During a press conference Sunday afternoon, President Obama called the attack an "act of terror" and called it "the most deadly shooting in American history.

Obama ordered flags to be flown at half-staff at the White House and federal buildings until sunset Thursday "as a mark of respect for victims of the act of hatred and terror." He's also directing the same observance at embassies and other U.S. government facilities abroad.

At a news conference Sunday morning, authorities labeled the situation as a domestic terrorism situation. CNN reported investigators are considering the attack a possible hate crime.

WHAT HAPPENED:

The rampage started around 2 a.m. Orlando time Sunday at Pulse nightclub, a club that bills itself as a gay nightclub in the downtown area.  About 300 people were likely inside the club at the time of the shooting.

Police say Mateen opened fire on patrons early Sunday. He also exchanged fire with an officer working at the club. Police say Mateen then went back inside and took hostages. Police sent in a SWAT team to rescue hostages about 5 a.m. and Mateen died in an exchange of gunfire with SWAT officers. Thirty people were rescued from inside the club.

Police say 11 officers exchanged gunfire with the shooter. Also, officials say three deputy sheriffs actively engaged, and fired their weapons. They're relieved of duties pending an investigation. That's typical procedure in such cases.

SECOND DEADLY SHOOTING IN TWO DAYS:

The attack follows the fatal shooting late Friday of 22-year-old singer Christina Grimmie, who was killed after her concert in Orlando by a 27-year-old Florida man who later killed himself. Grimmie was a YouTube sensation and former contestant on "The Voice."

CANDIDATES BEGIN GUN DEBATE:

Donald Trump isn't pausing his political commentary for the biggest mass shooting in U.S. history.

Trump tweeted as Obama began speaking: "Is President Obama going to finally mention the words radical Islamic terrorism? If he doesn't he should immediately resign in disgrace!"

Is President Obama going to finally mention the words radical Islamic terrorism? If he doesn't he should immediately resign in disgrace!

— Donald J. Trump (@realDonaldTrump) June 12, 2016

The shooting has thrust the topic of gun control back into focus as a presidential election nears.

Obama says shooting is a further reminder of how easy it is for someone to get a weapon that allows them to shoot people in a school, in a house of worship, a movie theater or a gay nightclub. Speaking from the White House, Obama says the United States has to decide if that is the "country we want to be." He says that doing nothing is a decision as well.

Hillary Clinton has called for expanding background checks to sales at gun shows and online purchases, and for reinstating a ban on assault weapons. Trump said the existing background check system should be fixed, not expanded, and that assault-weapons bans do not work.

IN OUR AREA:

Louisiana Governor John Bel Edwards released a statement about the shooting:

"There are no words that will comfort the survivors and families of the victims of this tragic incident, but it is our hope that the people of Florida will find solace in this scripture during this very difficult time. This is a senseless tragedy of unimaginable scale. In the face of adversity, as we always do, we stand united against acts of terrorism that threaten our people and our way of life. Donna and I, along with every citizen in Louisiana, send our thoughts and prayers to the victims and their families. We stand ready to support the State of Florida in any way that we can to bring justice for those whose lives were lost."

Edwards, Senate President John Alario, House Speaker Taylor Barras, and members of the Louisiana Legislature will participate in a “Moment of Unity."  The event will take place at 1 p.m. Monday in the rotunda of the Louisiana State Capitol.

Capital City Alliance and other LGBT organizations plan to hold a vigil to pay respect to the shooting victims. The event is planned for Monday night between 6 p.m. to 7 p.m.

ONE DAY AFTER THE SHOOTING:

On Monday, the city released a list containing the names and ages of the victims of the nightclub shooting who have had their next of kin notified. The list will be periodically updated on www.cityoforlando.net/blog/victims/ as those who died are identified and families and loved ones notified. The city gave no additional information other than the names.

- Edward Sotomayor Jr., 34
- Stanley Almodovar III, 23
- Luis Omar Ocasio-Capo, 20
- Juan Ramon Guerroro, 22
- Eric Ivan Ortiz-Rivera, 36
- Peter O. Gonzalez-Cruz, 22
- Luis S. Vielma, 22
- Kimberly Morris, 37
- Eddie Jamoldroy Justice, 30
- Darryl Roman Burt II, 29
- Deonka Deidra Drayton, 32
- Alejandro Barrios Martinez, 21
- Anthony Luis Laureanodisla, 25
- Jean Carlos Mendez Perez, 35
-Franky Jimmy Dejesus Velazquez, 50
- Amanda Alvear, 25
- Martin Benitez Torres, 33
- Luis Daniel Wilson-Leon, 37
- Mercedez Marisol Flores, 26
- Xavier Emmanuel Serrano Rosado, 35
- Gilberto Ramon Silva Menendez, 25
- Simon Adrian Carrillo Fernandez, 31
- Oscar A Aracena-Montero, 26
- Enrique L. Rios, Jr., 25
- Miguel Angel Honorato, 30
- Javier Jorge-Reyes, 40
- Joel Rayon Paniagua, 32
- Jason Benjamin Josaphat, 19
- Cory James Connell, 21
- Juan P. Rivera Velazquez, 37
- Luis Daniel Conde, 39
- Shane Evan Tomlinson, 33
- Juan Chevez-Martinez, 25
- Jerald Arthur Wright, 31
- Leroy Valentin Fernandez, 25
- Tevin Eugene Crosby, 25

Hospital officials in Florida listed five people in "grave condition" late Monday morning after they were wounded in the attack at the nightclub. According to Orlando Regional Medical Center, 29 people remain at the hospital in total with a number of the patients remaining critically ill or in a state of shock. Monday will see doctors carry out six more surgeries a day after the shooting that took the lives of 50 people including the shooter.

News 2 will carry the 1 p.m. "Moment of Unity" mentioned earlier in this story on Facebook Live. Check back with this story throughout the day as more details are released.